# Q | Using Regex and eachmatch() to extract substrings

**URL:** https://discourse.julialang.org/t/q-using-regex-and-eachmatch-to-extract-substrings/97128
**Category:** General Usage
**Tags:** question, regex
**Created:** [April 5, 2023, 6:36pm UTC](https://discourse.julialang.org/t/q-using-regex-and-eachmatch-to-extract-substrings/97128 "2023-04-05T18:36:52Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![Audrius-St](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/audrius-st/32/24175_2.png) [@Audrius-St](https://discourse.julialang.org/u/Audrius-St)
#### Post date: [April 5, 2023, 6:36pm UTC](https://discourse.julialang.org/t/q-using-regex-and-eachmatch-to-extract-substrings/97128/1 "2023-04-05T18:36:52Z")

</div>

Hello,

I’m using a package [[Form 4.3.0](https://github.com/vermaseren/form)] for symbolic code optimization that outputs results in C and have written a script to convert the code to Julia.

It’s worked to-date, however, I’ve run into a new problem in recent use which is summarized in the following MWCE:

```julia
# test_string_match.jl

begin
    # c_rhs_str = "x*pow(w[2],4)"
    c_rhs_str = "pow(x,2)*pow(w[2],4)"

    rgx = r"pow\((.*),(.*[^.*])\)"

    regex_match = collect(eachmatch(rgx, c_rhs_str, overlap = false))

    for ith_match in regex_match
        @show pow_substr = ith_match.match
        @show rgx_vrbl, rgx_expnt = match(rgx, pow_substr)
    end
end

```

```julia
c_rhs_str = "x*pow(w[2],4)" = "x*pow(w[2],4)"
pow_substr = ith_match.match = "pow(w[2],4)"
(rgx_vrbl, rgx_expnt) = match(rgx, pow_substr) = RegexMatch("pow(w[2],4)", 1="w[2]", 2="4")

```

gives the expected result, however,

```julia
c_rhs_str = "pow(x,2)*pow(w[2],4)" = "pow(x,2)*pow(w[2],4)"
pow_substr = ith_match.match = "pow(x,2)*pow(w[2],4)"
(rgx_vrbl, rgx_expnt) = match(rgx, pow_substr) = RegexMatch("pow(x,2)*pow(w[2],4)", 1="x,2)*pow(w[2]", 2="4")

```

does not give the result I thought I would get

> pow\_substr = ith\_match.match = “pow(x24)”  
> (rgx\_vrbl, rgx\_expnt) = match(rgx, pow\_substr) = RegexMatch(“pow(x,4)”, 1=“x”, 2=“2”)  
> pow\_substr = ith\_match.match = “pow(w[2],4)”  
> (rgx\_vrbl, rgx\_expnt) = match(rgx, pow\_substr) = RegexMatch(“pow(w[2],4)”, 1=“w[2]”, 2=“4”)

with the two `pow()` parsed into separate substrings.

So I’m wondering if this is a problem with my use of Regex or eachmatch() or both?

---

<div class="post-metadata">

### Author: ![Jollywatt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jollywatt/32/202198_2.png) [@Jollywatt](https://discourse.julialang.org/u/Jollywatt)
#### Post date: [April 5, 2023, 8:06pm UTC](https://discourse.julialang.org/t/q-using-regex-and-eachmatch-to-extract-substrings/97128/2 "2023-04-05T20:06:45Z")

</div>

This doesn’t answer your regex question, but it looks like Form output is largely valid Julia syntax. Perhaps you need to do a few minor transformations like `replace(s, "**"=>"^")`, but assuming you have, you could use `Meta.parse(s)` to convert it to (quoted) Julia code.